Lecture 11 Flashcards
(12 cards)
phenotypic variance
Vp
- dispersion of measurable trait resulting from an interaction between its genotype and its environment
- stabilizing and disruptive selection can change Vp
genotype
the alleles (A1A2, B1B1, etc) present at a genetic locus (or loci)
what is inherited
heritability
h^2 measures how much of the variation in a trait is due to genetics
- estimated by comparing trait similarities between parents and offspring
what is the breeders equation
R = h^2 x S
R = response to selection
S = selection differential
h^2 = hertiablilty
response to selection (R)
the difference between the mean trait value of offspring and the mean trait value of the original population before selection
- measures how much the trait actually changes in the next generation
how much the finch population evolves depends on:
- selection differential (S)
- heritability
what does the breeders equation calculate
predicts how much a trait will change in the next generation (R) based on how strong selection is (S) and how much of the trait is inherited (h²).
What is directional selection?
Directional selection favors an increase or decrease in the mean of a trait over time.
What is stabilizing selection?
Stabilizing selection favors average values of a trait, reducing extreme variations.
What do long-term studies reveal about natural selection?
The direction and strength of natural selection can fluctuate over time based on environmental changes.
What does narrow-sense heritability (ℎ2) include?
It includes only additive genetic effects, meaning how genes at different loci contribute to trait variance.
Are evolution and natural selection the same?
No! Selection can occur without evolution if heritability (ℎ2) is zero, selection can favour certain individuals but their offspring won’t inherit the trait
- for natural selection to cause evolution the trait must be heritable
